Exposure of M1.WT1 +KTS cells to LIF results in the rapid suppression of proliferation and clonogenicity associated with the induction of terminal macrophage differentiation. M1 cell populations were cultured in the presence or absence of LIF (1 ng/mL) for the indicated timepoints and assessed for: (A) cellular proliferation as determined by counting viable cell numbers on eosin dye exclusion; (B) clonogenic potential as determined by colony formation in soft agar in the absence of LIF; and (C) differentiation as determined by Leishman's staining of cytospin preparations and scoring the proportion of blast cells to cells at intermediate monocytic and mature macrophage stages. (▪), M1 +LIF; (□), M1 −LIF; (▴), M1.Neo +LIF; (▵), M1.Neo −LIF; (⧫), M1.WT1.1 (+/+) +LIF; (◊), M1.WT1.1 (+/+) −LIF; (•), M1.WT1.2 (−/+) +LIF; (○), M1.WT1.2 (−/+) −LIF.